Sonny Bill Williams has been granted a special exemption to be picked for the All Blacks' end of year tour.

New Zealand Rugby Union chief executive Steve Tew confirmed on Monday Williams would not need to play in the National Provincial Championship following his commitments with the Sydney Roosters in the NRL.

NZRU rules state that players must take part in the preceding domestic competition in order to be eligible for the All Blacks.

However, the board voted on Friday to make an exemption for Williams should he not be able to make an appearance for Counties-Manukau either due to the length of the Roosters season, or injury.

If that's the case, his selection for the tour of the United States and Europe in November will be left to the discretion of All Blacks coach Steve Hansen.

Tew stressed the exemption may not be necessary.

''It is still expected he will play ITM Cup rugby, but that is dependent on how the Roosters do in the NRL, and if you ask Warriors fans they would say they are doing quite well,'' he said in reference to the Roosters 46-12 weekend win over the Auckland NRL club.

''The board were asked on Friday what they were comfortable with in terms of how many games he had to play to tick the [All Blacks eligibility] box.

"The board were of the view, which we completely concur with, that we have made a big investment in Sonny Bill Williams and if the coaches believe we get the most out of that investment by taking him on the tour in November then they should have the discretion to do so.

''There were a number of unknowns around the situation which made it sensible to leave some flexibility.

''That's entirely in the hands of the All Blacks coaches and Sonny Bill himself because he will have to make an assessment about whether touring at the end of the year is the best thing for him or not depending on how the [Roosters] season pans out from here.

''If he were not to play [for Counties Manukau] the board have the discretion to allow him not to play and they have exercised that discretion in advance, but it is still anticipated he will play ITM Cup because we think that will be of benefit to him anyway.''

The Roosters season could finish as early as September 4, but if they reach the NRL grand final it could be as late as October 5.

That could potentially leave Williams with just one week to cram in a game for the Steelers, who play Auckland in Pukekohe on October 8 and Tasman four days later in Blenheim.

Tew noted that Williams does meet the NZRU's other All Blacks eligibility criteria.

''You have to be contracted, you have to have shown the commitment to be in New Zealand going forward, and you have to play in a competition preceding the tour to be eligible.

''He clearly ticks the first two boxes because he will live in New Zealand in 2015-16 and he is contracted to this organisation for that period of time.''

It would not be the first time the NZRU have used their discretion to waive the requirement to select a player returning from off shore with Luke McAlister selected in similar circumstances 2009 after returning from Europe.